The present invention is in the field of pulmonary delivery of bioactive molecules.
Due to their large size, most macromolecules are delivered by injection, and noninvasive delivery systems usually do not work. Although some digestion resistant small peptides, such as 1-desamino-8-D-arginine vasopressin (DDAVP; a nine amino acid vasopressin analog) and cyclosporine (11 amino acids), have been delivered successfully by an oral route, proteins or peptides are usually degraded by enzymes in the stomach or intestine. The skin offers an even less naturally permeable boundary to macromolecules than the gastrointestinal tract, and passive transdermal delivery of proteins and peptides using xe2x80x9cpatchxe2x80x9d technology has had limited success.
Drug delivery by inhalation represents a well established mode of administration of low molecular weight pharmaceuticals for various lung disorders, with a promise for noninvasive systemic delivery of drugs in general. Several biopharmaceutical companies are developing methods for pulmonary delivery of peptides and proteins, with one such product already in clinical use (the enzyme DNAse produced by Genentech for the treatment of symptoms of cystic fibrosis in children).
The lung is an attractive target for noninvasive delivery of proteins. Many proteins readily and naturally absorb through the deep lung into the bloodstream. The expanded deep lung of an adult human has a large surface area of about 100 m2 with a potential for high bioavailability. In addition, the lung is a robust organ which, for instance, can successfully cope with at least 10 mg of nuisance dusts in the workplace each day for years. Furthermore, there is no evidence that inhaling autologous proteins presents significant immune issues.
A number of pharmaceutical preparations for pulmonary delivery of drugs has been developed. For example, U.S. Pat. No. 5,230,884 to Evans et al., discloses the use of reverse micelles for pulmonary delivery of proteins and peptides. Reverse micelles are formed by adding a little water to a nonpolar solvent (e.g. hexane) to form microdroplets. In this medium, a surfactant (detergent) will orient itself with its polar heads inward, so that they are in contact with the water and the hydrophobic tails outward. Thus the tiny droplets of water are surrounded by surfactant. The protein to be delivered is dissolved in the aqueous phase.
U.S. Pat. No. 5,654,007 to Johnson et al., discloses methods for making an agglomerate composition containing a medicament powder (e.g. proteins, nucleic acids, peptides, etc.) wherein a nonaqueous solvent binding liquid (a fluorocarbon) is used to bind the fine particles into aggregated units. The agglomerate composition has a mean size ranging from 50 to 600 microns and is allegedly useful in pulmonary drug delivery by inhalation.
PCT/US97/08895 by Massachusetts Institute of Technology discloses particles made of a biodegradable material or drug, which have a tap density less than 0.4 g/cm3 and a mean diameter between 5 xcexcm and 30 xcexcm.
PCT/EP97/01560 by Glaxo Group Limited discloses spherical hollow drug particulates for use in pulmonary delivery.
At present, clinically approved systems for pulmonary delivery of biomacromolecules are limited to using either dry powders or aqueous solutions; which are aerosolized, and the resultant xe2x80x9cmistxe2x80x9d is inhaled by a patient. These approaches, while feasible, may suffer from serious drawbacks. See a review in Nature Biotechnology 16, 141-143 (1998) for a more detailed discussion. For example, the problems with powders include their hygroscopicity, clump formation, and irreproducibility. Aqueous solutions of proteins and nucleic acids are free of these shortcomings but are difficult to aerosolize (due to the high boiling point of water) and susceptible to microbial attack.
It is therefore an object of the present invention to provide a minimally invasive delivery method for bioactive agents.
It is another object of the present invention to provide a means for pulmonary delivery of bioactive agents.
Methods and formulations for delivery of macromolecules, such as proteins, polysaccharides, and nucleic acids, are disclosed, where the macromolecule is dissolved or dispersed in a low toxicity organic solvent which can be aerosolized for delivery to a patient""s lungs by inhalation. Optionally, appropriate solubility enhancers are also present in the formulations composition.
Definitions
The term low toxicity as used herein refers to a solvent that does not cause permanent long term damage to body cells or organs.
The term aerosol as used herein refers to any preparation of a fine mist of particles, typically less than 10 microns in diameter, which can be in solution or a suspension, whether or not it is produced using a propellant. Aerosols can be produced using standard techniques, such as ultrasonication or high pressure treatment]
The terms solution or dissolve as used herein refer to compositions in which the bioactive agent is present as a monomolecular dispersion. Concentration ranges are from 0 to 500 mg/ml.
Residual solvents in pharmaceuticals are organic volatile chemicals that are used or produced in the syntheses of drug substances, or excipients, or in the preparation of drug products which are not completely removed by processing.
Biocompatible refers to Class 3 residual solvents that do not cause any long term harmful effects on bodily tissues or cells. This is defined in the U.S. Federal Register vol. 62, number 85, pages 24301-24309 as solvents with low toxic potential to man; no health based exposure limit is needed. Class 3 solvents have PDE""s of 50 mg or more per day.
As used herein, the term xe2x80x9csurfactantxe2x80x9d refers to any agent which preferentially adsorbs to an interface between two immiscible phases, such as the interface between water and an organic polymer solution, a water/air interface or organic solvent/air interface.
1. Compositions
Active Ingredients
The formulations disclosed herein can be used for the delivery of a variety of molecules, especially macromolecules. Smaller molecules can also be delivered as well. Macromolecules are generally defined as molecules having a molecular weight of greater than about 1000 daltons. Examples of macromolecules include proteins and large peptides, polysaccharides and oligosaccharides, and DNA and RNA nucleic acid molecules and their analogs having therapeutic, prophylactic or diagnostic activities. Nucleic acid molecules include genes, antisense molecules that bind to complementary DNA to inhibit transcription, and ribozymes. The agents to be incorporated can have any of a variety of biological activities, being, for example vasoactive agents, neuroactive agents, hormones, anticoagulants, immunomodulating agents, cytotoxic agents, prophylactic agents, antibiotics, antivirals, antisense, antigens, or antibodies.
Proteins are defined as consisting of 100 amino acid residues or more; peptides are less than 100 amino acid residues. Unless otherwise stated, the term protein refers to both proteins and peptides as well as peptidomimetic compounds (i.e. peptide-like substances having some non-peptide groups). Examples of proteins include insulin and other hormones. An example of an polysaccharide is heparin.
The formulations may include an active ingredient for local delivery within the lung, or for systemic treatment. For example, formulations for local delivery may be used to treat asthma, emphysema or cystic fibrosis. Representative agents include genes encoding enzymes to treat cystic fibrosis and beta agonists for treatment of asthma. Agents having systemic effects include, but are not limited to, insulin, calcitonin, human growth hormone, erythropoietin (xe2x80x9cEPOxe2x80x9d), DNAse, leuprolide (or gonadotropin-releasing hormone (xe2x80x9cLHRHxe2x80x9d)), granulocyte colony-stimulating factor (xe2x80x9cG-CSFxe2x80x9d), parathyroid hormone-related peptide, somatostatin, testosterone, progesterone, estradiol, nicotine, fentanyl, norethisterone, clonidine, scopolomine, salicylate, cromolyn sodium, salmeterol, formeterol, albuterol, and valium.
Solvents
The solvents useful in the compositions are low toxicity organic (i.e. nonaqueous) class 3 residual solvents, such as ethanol, acetone, ethyl acetate, tetrahydofuran, ethyl ether, and propanol. The solvent is selected based on its ability to readily aerosolize the composition. The solvent should not detrimentally react with the active ingredient. An appropriate solvent should be used that dissolves the active ingredient or forms a suspension of the active ingredient. A suspension is also referred to as a dispersion herein.
The solvent moreover should be sufficiently volatile to enable formation of an aerosol of the solution or suspension. Additional solvents or aerosolizing agents, such as freons, can be added as desired to increase the volatility of the solution or suspension.
Concentration
Macromolecules, such as proteins and nucleic acids can be dissolved in some organic solvents, e.g. in ethanol, at relatively high concentrations provided that certain critical guidelines are followed. For example, the protein is preferably lyophilized from an aqueous solution having a pH different, preferably remote, from the isoelectric point of the protein. See Bromberg and Klibanov, Proc. Natl. Acad. Sci. USA, 92, 1262-1266 (1995), the disclosure of which is incorporated herein by reference. The solubility of macromolecules in organic solvents can be enhanced by certain additives, such as some inorganic salts, detergents, and water soluble polymers such as poly(ethylene glycol) and carboxymethylcellulose. Alternatively, biomacromolecular dispersions or suspensions in the form of microcrystals or lyophilized powders suspended in organic solvents can be used to make aerosols for pulmonary delivery. Proteins are usually not irreversibly damaged in such systems. The advantages of the nonaqueous formulations for pulmonary delivery include stability against microbial contamination and a greater (compared to water) ease of the aerosol formation due to their volatility.
Preferably the active ingredient is dissolved or dispersed to a concentration of between 0 and 500 mg/ml, more preferably between 1 mg/ml and 100 mg/ml, and most preferably between 10 xcexcg/ml and 10 mg/ml. The same concentrations can be used as have been used for aqueous solutions delivered via the pulmonary route. The concentration will be determined by the solubility or dispersibility of the macromolecule and the amount of solution or dispersion that can be safely administered. The concentration is also limited by the fact that the solution or suspension needs to be aerosolized. Desired dosages are known for many macromolecules and can be determined by means known to those skilled in the art. Many protein and peptide drugs require deep lung delivery of two to 20 mg per dose. Patton et al., xe2x80x9cBreathing Life into Protein Drugsxe2x80x9d, Nature Biotechnology 16:141-143 (February 1998). Since the volume of drug containing solution or suspension delivered to the patient is preferably about 1 to 5 ml, the concentration will preferably be from about 0.4 to 20 mg per ml.
Surfactants and Other Ingredients
The formulations may optionally include a surfactant to enhance solubility or absorption. Surfactants generally possess a hydrophilic moiety and a lipophilic moiety, such that, upon absorbing to microparticles, they tend to present moieties to the external environment that do not attract similarly-coated particles, thus reducing particle agglomeration. Surfactants may also promote absorption of a therapeutic or diagnostic agent and increase bioavailability of the agent.
Synthetic or naturally occurring surfactants known in the art, can be used. Surfactants which can be included in the formulation to improve their aerosolization properties include phosphoglycerides. Exemplary phosphoglycerides include phosphatidylcholines, such as the naturally occurring surfactant, L-xcex1-phosphatidylcholine dipalmitoyl (xe2x80x9cDPPCxe2x80x9d). The use of surfactants endogenous to the lung may avoid the need for the use of non-physiologic surfactants. Other exemplary surfactants include diphosphatidyl glycerol (DPPG); sodium dodecyl sulfate (SDS), derivatives of polyethylene glycol (PEG); polyoxyethylene-9-lauryl ether; a surface active fatty acid, such as palmitic acid or oleic acid; sorbitan trioleate (Span 85); glycocholate; surfactin; poloxomers; sorbitan fatty acid esters such as sorbitan trioleate; tyloxapol and a phospholipid; and alkylated sugars such as octyl glucoside. These are added to the solution or dispersion to a concentration above the surfactant""s critical micelle concentration (CMC). Concentrations will typically be between 0.001% and 10%.
The surfactant can also be used as a particle stabilizer for suspensions. Other additives, such as some inorganic salts (10 mM to 5 M), and viscosity modifying agents such as the water soluble polymers poly(ethylene glycol) and carboxymethylcellulose (0.1% to 10% (w/v)), may also be used to enhance solubility, stability or absorption.
2. Methods for Making the Compositions
The compositions are made by mixing the macromolecule to be delivered with a suitable biocompatible organic solvent to form a solution or dispersion of the macromolecule. Additional ingredients, such as surfactants and other excipients, both optional, can be added as desired, to improve solubility and delivery, for example. The solvent is selected as described above. Preferably, the macromolecule is lyophilized from an aqueous solution that has a pH different from the pI of the macromolecule, before being dissolved or dispersed in the solvent.
3. Methods for Using the Compositions
The compositions can be delivered by any method and/or device which is currently used for pulmonary delivery. For example, nebulizer can be used. Nebulizers create a fine mist from a solution or suspension, which is inhaled by the patient. The devices described in U.S. Pat. No. 5,709,202 to Lloyd, et al., can be used. A metered dose inhaler (MDI) can also be used. An MDI typically includes a pressurized canister having a meter valve, wherein the canister is filled with the solution or suspension and a propellant. The solvent itself may function as the propellant, or the composition may be combined with a propellant, such as freon. The composition is a fine mist when released from the canister due to the release in pressure. The propellant and solvent may wholly or partially evaporate due to the decrease in pressure.
The present invention is further described by the following non-limiting example.